Method for composite flow molding

ABSTRACT

An apparatus for molding a part includes a plunger cavity, a plunger, and a mold cavity, wherein the plunger is oriented out-of-plane with respect to a major surface of the mold cavity, and first and second vents couples to respective first and second portions of the mold cavity. In a method, resin and fiber are forced into the mold cavity from a plunger cavity, and at least some of the fibers and resin are preferentially flowed to certain region in the mold cavity via the use of vents.

STATEMENT OF RELATED CASES

This case claims priority of U.S. Pat. App. Ser. No. 62/743,390 filedOct. 9, 2018, which is incorporated by reference herein.

FIELD OF THE INVENTION

This disclosure relates generally to molding complex parts, particularlythose with very small, thin, or intricate features.

BACKGROUND

It is often desirable to fabricate parts from fiber-composite materials.A fiber composite part includes fibers that are dispersed within amatrix, formed from a resin. The matrix surrounds and supports thefibers by maintaining their relative positions, in addition topreventing the fibers from abrasion and environmental attack. The fibersimpart their mechanical and physical properties to enhance those of thematrix. The combination is synergistic; the composite possesses materialproperties unavailable from the individual constituents, such as a veryhigh strength-to-weight ratio.

A variety of different molding processes are available to formfiber-composite parts, such as compression molding, filament winding,pultrusion, wet layup, and transfer molding. There are, however,challenges to using such processes for fabricating complex parts withvery small, thin, or intricate features, particularly those requiringsubstantial strength and stiffness.

SUMMARY

The present invention provides a method for fabricating fiber-reinforcedparts having very small, thin, or intricate features, as well as desiredproperties. Such parts might have feature sizes that are too small/thinto accommodate bent preforms, yet, at the same time, require continuousfibers for strength and stiffness.

In accordance with the present teachings, preforms are placed on aportion of a mold cavity. A preform is a sized, or sized and shapedbundle of fiber. In the illustrative embodiment, the bundle of fibercontains thousands of fibers, and is typically referred to as “tow.” Inthe illustrative embodiment, the fibers in the tow are (pre-)impregnated with a polymer resin; the tow is then called “towpreg” or“prepreg tow.”

The preforms are compressed and heated, which melts the resin therein.In the illustrative embodiment, the compression is applied by a plungerthat moves linearly within a plunger cavity, wherein the stroke axis(direction) of the plunger is oriented at least 45 degrees out-of-planewith respect to a major surface of the mold cavity. In the illustrativeembodiments, the major surface of the mold cavity is substantiallyorthogonal to the plunger's stroke axis.

Embodiments of the invention enable a level of control of fibermovement/placement that is not possible with prior-art molding processesthat utilize a plunger. In the prior art, particularly withinjection-molding processes, chopped fiber is used as feedstock. As thechopped fiber is forced into a mold via a plunger, it rotates and turnsbased on the movement of resin through the mold cavity, as well ascollisions with a complex and random matrix of other fibers. Inembodiments of the invention, however, the feed comprises a majority ofrelatively long fibers (i.e., fibers that are comparable to the lengthof a major axis of the part being formed). It is believed that the useof long fibers stabilizes the underlying fiber structure of the partbecause the fibers are kept under some degree of tension due to featuresof the process, such that the fibers do not strictly follow the flow ofthe liquid resin. Rather, fiber position and orientation in the moldcavity and, hence, the final part, are controlled, to a substantialdegree, by characteristics of the fiber (e.g., length, orientation inthe plunger cavity, etc.), rather than the liquefied resin.

In embodiments of the method, the preforms are oriented such that:

-   -   they align with the stroke direction of the plunger; or    -   they align with a plane that is orthogonal to the stroke        direction of the plunger; or    -   some align with, and some are within a plane that is orthogonal        to, the stroke direction of the plunger;    -   they align with one or more planes that are parallel to a major        surface of the mold cavity; or    -   they neither align with, nor align with a plane that is        orthogonal to, the stroke direction of the plunger.

For preforms that align with one or more planes that are parallel to amajor surface of the mold cavity, in some embodiments of the method:

-   -   they are aligned with the long(est) axis of the mold cavity        (i.e., the “axial” direction); or    -   they are transverse (in-plane and orthogonal) to the long(est)        axis of the mold cavity (i.e., the “transverse” direction); or    -   some align with the axial direction and some align with the        transverse direction; or    -   they are oriented at a non-zero angle with respect to the axial        direction and transverse direction; or    -   they are segregated into at least two groups that are oriented        at different non-zero angles with respect to the axial direction        and transverse direction.

In various embodiments, the preforms include:

-   -   continuous fiber (i.e., fiber as long as the longest axis of the        mold cavity); or    -   shorter fiber (i.e., fiber having a length similar to that of        smaller features of the mold cavity); or    -   mixtures of both continuous and shorter fibers.

Fibers tend, to some degree, to align with the direction of flow throughthe mold cavity. Also, fibers flow to areas of relatively lowerpressure. Consequently, the inventors realized that fibers, whenappropriately sized, can be directed into very thin, small, or otherwiseintricate features, or their final orientation in the part can beengineered. Key parameters in that regard is the size of the fiber(i.e., comparable to the size of the small feature) as well as theselective placement and actuation of vents, which can alter the flow ofresin and fiber through the mold cavity.

In accordance with some embodiments, the final location of fibers in amold cavity during plunger-driven compression molding, and, hence, theirfinal location in the part being fabricated, can be controlled throughthe use of one or more of the following parameters, as a function ofapplication specifics:

(a) fiber length;

(b) the orientation of fibers in the plunger cavity;

(c) the order in which fibers (preforms) are stacked in the plungercavity;

(d) the incorporation of vents, and their specific placement in the moldcavity;

(e) the sequencing of vent actuation.

The feedstock (i.e., preforms) is placed in the plunger cavity. In someembodiments, the preforms are stacked in successive layers in theplunger cavity. After the resin has melted (due to applied heat/energy),advancing the plunger through the plunger cavity forces fiber and meltedresin into the mold cavity. In some embodiments, vents are opened andclosed multiple times during a single plunger stroke. The use of thevents enables pressure to be selectively reduced in desired regions of amold cavity, which will facilitate directing the flow of resin and fiberto such reduced-pressure regions.

In accordance with some embodiments of the method, sequencing theactuation of the vents enables different layers/groups of preforms inthe stack thereof to be directed to different areas of the mold cavity.

For example, consider a mold cavity in which there is a first ventproximal to a first feature of the mold cavity and a second ventproximal to a second feature of the mold cavity. To selectively directfiber to the first feature, the first vent is opened. To selectivelydirect fiber to the second feature, the second vent is opened some timeafter the first vent. If, for example, the first feature of the moldcavity is a relatively small compared to the overall size of the moldcavity, the fibers intended for that region will be smaller than thosedirected to the major regions of the mold cavity. More particularly,these smaller fibers will be comparable to the size of the first(relatively small) feature. Typically, the smaller fibers will besomewhat longer than the feature to facilitate overlap between thosefibers with longer fibers in the major regions of the cavity. Suchoverlap enhances part strength.

Typically, the first vent does not need to be closed before opening thesecond vent. In particular, as the first feature fills with fiber andresin, the pressure required to force more material into that featureincreases dramatically. Thus, once the second vent opens, material willflow towards the second feature, since the pressure will be lower therea fiber and resin will readily flow thereto. In this example, theopening of the first vent and, after a period of time, the opening ofthe second vent, both occur during a single plunger stroke.

Furthermore, the orientation of fibers in the mold cavity and, hence,the final part, can be influenced by the orientation of the preforms.Such orientations include the orientation of the preforms (fibers): (1)relative to the stroke direction of the plunger, and/or (2) relative tothe axes of the mold. Controlling fiber orientation using theseparameters enables off-axis directions of a part to be strengthened.

Moreover, based on the aforementioned ability to control the endlocation of fibers in the mold cavity, a modulus gradient (i.e., agradient in Young's modulus) can be established through a part. This canbe accomplished, for example, using preforms that differ in fiber type(e.g., some including carbon fiber, others including glass fiber, etc.),and by appropriately organizing them in the stack within the plungercavity. In conjunction with the selective actuation of vents, thedifferent materials wind up at different locations in the mold cavity.

Alternatively, a modulus gradient can be created by controlling thefiber volume fraction. For example, a first group of preforms can beformed such that the fiber volume fraction is relatively greater thanthat of a second group of preforms (i.e., there is relatively lessresin, as a percentage of the total constituents in the first group ofpreforms than in the second group of preforms). Using the aforementionedmentioned technique of selective actuation of vents, in conjunction withappropriately stacking the first and second groups of preforms in themold cavity, the resin and fiber from the first group of preforms can bedirected to a first location in the mold, and the resin and fiber fromthe second group of preforms can be directed to a second location in themold. This results in the creation of a relatively more fiber-richregion in the first location of the mold, and, hence, the final part,thereby creating the aforementioned modulus gradient.

Also, the strength and stiffness of selected areas of a part can becontrolled by using preforms having different lengths. Those parameterscan be altered as a function of the extent of fiber overlap in specificregions of the part (i.e., the amount by which longer fibers in the mainportion of the part overlap with potentially smaller fibers in asmaller/intricate feature of the part. Once again, this is implementedthrough the use and selective actuation of vents, and appropriatestacking of preforms having fibers of different lengths and, in someapplications, different orientations with respect to the plunger cavityand/or mold cavity.

In summary, some embodiments of the invention utilize a plunger that isout-of-plane with respect to a mold cavity in conjunction with molds forthe fabrication of parts via compression molding. In some embodiments,vents are additionally used to assist in directing the movement offibers to specific regions of the mold cavity. Although vents andplungers are known in the prior art, typically for use in injectionmolding, such use is distinct from embodiments of the invention. Unlikethe prior art, applicants disclose, for some embodiments:

-   -   the sequenced actuation of vents, which directs the flow of        fibers and resin to specific locations in a mold cavity;    -   the use of differentiated preforms (e.g., different lengths,        different materials, different orientation, etc.) for molding a        part;    -   the use of ordered preform stacking, wherein the differentiated        preforms are stacked in a particular order in the mold's plunger        cavity; and    -   coordinating sequenced vent actuation with ordered preform        stacking.

The techniques provide an unprecedented measure of control over fiberplacement in the mold cavity and, hence, a part being molded. Suchteachings were unknown in the prior art. Consider, for example, that thefeedstock to an injection-molding process is typically homogenous, suchthat in addition to there being no concept of directing feedstock todifferent regions in a mold cavity, there was no reason to do so, sincethe feedstock was undifferentiated.

In accordance with the present teachings, preforms are placed in theplunger cavity. The lowest layer of preforms rests on a portion of themold cavity. The plunger's stroke axis is out-of-plane to a majorsurface of the mold cavity. In the illustrative embodiment, theplunger's stroke axis is 90 degrees out-of-plane (i.e., orthogonal) to amajor surface of the mold cavity. In some other embodiments, theplunger's stroke axis is greater than 45 degrees out-of-plane to a majorsurface of the mold cavity. By virtue of the orientation ofplunger/plunger cavity with respect to the mold, initial movement offibers in the mold cavity (as the fiber moves away from its position inthe stack) is via a shear force.

In a first embodiment, the invention provides a method comprising:advancing a plunger through a plunger cavity, the advancing plungerforcing liquefied resin and a plurality of fibers, sourced from aplurality of preforms, from the plunger cavity into a mold cavity;

preferentially flowing liquefied resin and a first group of fibers ofthe plurality thereof toward a first region in the mold cavity; and

after the liquefied resin and first group of fibers flow to the firstregion of the mold cavity, preferentially flowing liquefied resin and asecond group of fibers of the plurality thereof toward a second regionin the mold cavity.

In a second embodiment, and further to the first embodiment,preferentially flowing liquefied resin and a first group of fibersfurther comprises reducing pressure in the first region relative toother regions of the mold cavity.

In a third embodiment, and further to the second embodiment, reducingpressure in the first region further comprises actuating a first ventthat is fluidically coupled to the first region.

In a fourth embodiment, and further to the second embodiment,preferentially flowing liquefied resin and a second group of fibersfurther comprises reducing pressure in the second region relative toother regions of the mold cavity.

In a fifth embodiment, and further to the fourth embodiment, reducingpressure in the first region further comprises actuating a first ventthat is fluidically coupled to the first region; and reducing pressurein the second region further comprises actuating a second vent that isfluidically coupled to the second region.

In a sixth embodiment, and further to the first embodiment, theplurality of preforms comprises a first group of preforms having thefirst group of fibers and a second group of preforms having a secondgroup of fibers, wherein the first and second group of preforms differfrom one another as to at least one characteristic.

In a seventh embodiment, and further to the sixth embodiment, the atleast one characteristic is selected from the group consisting of alength of the fibers of the preforms, a composition of the fibers of thepreforms, and a fiber volume fraction of the preforms.

In an eighth embodiment, and further to the sixth embodiment, the onecharacteristic is a length of the fibers of the preforms, and whereinthe first group of preforms has relatively shorter fibers than thesecond group of preforms, the method further comprising sequencing thefirst group and second group of preforms in a stack in the plungercavity such that the first group is positioned relatively closer to themold cavity.

In a ninth embodiment, and further to the sixth embodiment, the spatialorientation of the first group of preforms and the second group ofpreforms in the plunger cavity differs from one another.

In a tenth embodiment, and further to the first embodiment, a methodfurther comprising adding a preform to the mold cavity before advancingthe plunger.

In an eleventh embodiment, and further to the sixth embodiment, themethod further comprises coordinating the order in which the first groupof preforms and the second group of preforms are stacked in the plungercavity with the sequence in which the first group of fibers and thesecond group of fibers are preferentially flowed toward respective firstand second regions of the mold cavity.

In a twelfth embodiment, the invention provides a method for moldingcomprising:

ordering, in a stack within a plunger cavity, first and second groups ofpreforms, each group comprising plural preforms, each preform comprisingresin-coated fibers, wherein the first group of preforms and the secondgroup of preforms differ from one another as to at least onecharacteristic;

liquefying the resin;

advancing a plunger through the plunger cavity to force, into a moldcavity, fibers and resin from the two groups of preforms; and

actuating, in sequence, a first vent and then a second vent, wherein:

-   -   the first vent is fluidically coupled to a first region of the        mold cavity, the second vent is fluidically coupled to a second        region of the mold cavity,    -   actuation of the first vent results in preferential flow of        fiber to the first region,    -   actuation of the second vent results in preferential flow of        fiber to the second region,

and wherein the ordering of preforms in the stack and the sequencing ofactuation of the vents are coordinated so that fibers from the firstgroup of preforms flow to the first region and fibers from the secondgroup of preforms flow to the second region.

In a thirteenth embodiment, and further to the twelfth embodiment, amethod comprising cooling the fibers and resin to create a compositepart.

In a fourteenth embodiment, and further to the twelfth embodiment,ordering, in a stack, further comprises providing a first spatialorientation to the first group of preforms and a second spatialorientation to the second group of preforms in the plunger cavity.

In a fifteenth embodiment, and further to the fourteenth embodiment, thefirst spatial orientation and the second spatial orientation areindividually selected from the group consisting of axially aligned withrespect to the plunger cavity, transversely aligned with respect to theplunger cavity, axially aligned with respect to the mold cavity,transversely aligned with respect to the mold cavity.

In a sixteenth embodiment, and further to the fourteenth embodiment, thefirst group of preforms and the second group of preforms aretransversely aligned with respect to the plunger cavity, and are neitherorthogonal nor parallel to one another.

In a seventeenth embodiment, the invention provides a method for moldingcomprising:

placing a first group of preforms in a first orientation in a plungercavity;

placing a second group of preforms in a second orientation in theplunger cavity, where the second group of preforms is placed on top ofthe first group of preforms;

advancing a plunger in the plunger cavity to force fibers and resin fromthe first group of preforms into a mold cavity;

directing fibers from the first group of preforms to a first region ofthe mold cavity;

advancing the plunger in the plunger cavity to force fibers and resinfrom the second group of preforms into the mold cavity; and

directing fibers from the second group of preforms to a second region ofthe mold cavity.

In a eighteenth embodiment, and further to the seventeenth embodiment,directing fibers from the first group of preforms to a first regionfurther comprises actuating a first vent that is fluidically coupled tothe first region of the mold cavity.

In a nineteenth embodiment, and further to the eighteenth embodiment,directing fibers from the second group of preforms to a second regionfurther comprises actuating a second vent that is fluidically coupled tothe second region of the mold cavity after the fibers from the firstgroup of preforms flow to the first region of the mold cavity.

In a twentieth embodiment, the invention provides a compression moldcomprising:

a plunger cavity;

a plunger that is received by the plunger cavity and moves linearlytherein;

a mold cavity, wherein a stroke axis of the plunger within the plungercavity is out-of-plane with respect to a major surface of the moldcavity, and wherein a cross-sectional area of a mouth of the plungercavity is substantially smaller than a cross-sectional area of the moldcavity;

a first vent that is fluidically coupled to a first portion of the moldcavity; and

a second vent that is fluidically coupled to a second portion of themold cavity.

In a twenty-first embodiment, and further to the twentieth embodiment,the first vent is coupled to a feature that is substantially smallerthan the major surface of the mold cavity.

In a twenty-second embodiment, and further to the twentieth embodiment,a length of the plunger cavity along the stroke axis is substantiallygreater than a depth of the mold cavity.

In a twenty-third embodiment, the invention provides a method formolding comprising:

placing a plurality of preforms in a plunger cavity, each preformincluding fibers coated with resin, a portion of which preforms resideon a surface of a mold cavity, wherein the surface is out-of-plane withrespect to the plunger and plunger cavity;

liquefying the resin; and

imparting, via a plunger moving through the plunger cavity, a shearforce to the fibers and liquefied resin, thereby causing the fibers andresin to flow through the mold cavity, wherein movement of at least someof the fibers aligns with an axial direction of the mold cavity.

In a twenty-fourth embodiment, and further to the twenty-thirdembodiment, placing the plurality of preforms in the plunger cavityfurther comprises aligning at least some of the preforms in a transversedirection with respect to the plunger cavity.

In a twenty-fifth embodiment, and further to the twenty-thirdembodiment, the plurality of preforms includes a first group of preformsand a second group of preforms, wherein the first and second groups ofpreforms differ in terms of a first characteristic.

In a twenty-sixth embodiment, and further to the twenty-fifthembodiment, the first characteristic is selected from the groupconsisting of a length of the fibers of the preforms, a composition ofthe fibers of the preforms, and a fiber volume fraction of the preforms.

In a twenty-seventh embodiment, and further to the twenty-sixthembodiment, the plurality of preforms are arranged in a stack in theplunger cavity, wherein the first group of preforms are relatively lowerin the stack and closer to mold cavity than the second group ofpreforms, so that the fibers from the first group of preforms flowthrough the mold cavity before fibers from the second of preforms.

In a twenty-eighth embodiment, and further to the twenty-seventhembodiment, a method comprising directing fibers from the first group ofpreforms to a first location in the mold cavity and directing fibersfrom the second group of preforms to a second location in the moldcavity.

In a twenty-ninth embodiment, and further to the twenty-eighthembodiment, the first location comprises a feature that is relativelysmaller than any feature associated with the second location.

In a thirtieth embodiment, and further to the twenty-fifth embodiment,the first group of preforms has a spatial orientation different than thesecond group of preforms with respect to at least one of either theplunger cavity and the mold cavity.

In a thirty-first embodiment, and further to the twenty-thirdembodiment, a method comprising adding a preform to the mold cavitybefore liquefying the resin.

In a thirty-second embodiment, and further to the twenty-thirdembodiment, a major portion of the fibers having a length that issubstantially as long as a major axis of the mold cavity.

In a thirty-third embodiment, and further to the twenty-thirdembodiment, a method comprising cooling mold cavity after the fibers andresin have flowed through the mold cavity.

In a thirty-fourth embodiment, the invention provides a method formolding comprising advancing a plunger through a plunger cavity, theadvancing plunger imparting a shear force to the liquefied resin and aplurality of fibers, thereby causing the fibers and resin to flowthrough the mold cavity, wherein movement of at least some of the fibersaligns with an axial direction of the mold cavity.

In a thirty-fifth embodiment, and further to the thirty-fourthembodiment, the plunger cavity is oriented out-of-plane by at least 45degrees with respect to a longest axis of the mold cavity.

In a thirty-sixth embodiment, and further to the thirty-fourthembodiment, the liquefied resin and plurality of fibers are sourced froma plurality of preforms that are situated in the plunger cavity.

In a thirty-seventh embodiment, and further to the thirty-sixthembodiment, the plurality of preforms includes at least two groups ofpreforms, wherein the two groups differ as to at least onecharacteristic.

In a thirty-eighth embodiment, and further to the thirty-seventhembodiment, the at least one characteristic relates to a composition ofthe preforms.

In a thirty-ninth embodiment, and further to the thirty-seventhembodiment, the least one characteristic relates to a spatialorientation of the preforms.

In a fortieth embodiment, and further to the thirty-seventh embodiment,a method comprising stacking the two groups of preforms in the plungercavity, wherein the stack is ordered, wherein the group of preformsfirst in order enters the mold cavity first and flows to a first regionin the mold cavity, and the group of preforms second in the order entersthe mold cavity second and flows to a second region in the mold cavity.

In a forty-first embodiment, the invention provides a compression moldcomprising:

a plunger cavity;

a plunger that is received by the plunger cavity and moves linearlytherein, and

a mold cavity, wherein a stroke axis of the plunger within the plungercavity is aligned with an axis that is out-of-plane with respect to amajor surface of the mold cavity, and wherein a cross-sectional area ofa mouth of the plunger cavity is substantially smaller than across-sectional area of the mold cavity.

In a forty-second embodiment, and further to the forty-first embodiment,the stroke axis of the plunger is ninety degrees out-of-plane withrespect to the major surface of the mold cavity.

In a forty-third embodiment, and further to the forty-first embodiment,the stroke axis of the plunger is in a range of ninety degrees toforty-five degrees out-of-plane with respect to a major surface of themold cavity.

In a forty-fourth embodiment, and further to the forty-first embodiment,a length of the plunger cavity along the stroke axis is substantiallylarger than a depth of the mold cavity.

In a forty-fifth embodiment, the invention provides a compression moldcomprising:

a plunger cavity;

a plunger that is received by the plunger cavity and moves linearlytherein, and

a mold cavity, wherein a length of the plunger cavity along the strokeaxis is substantially greater than a depth of the mold cavity.

In a forty-sixth embodiment, and further to the forty-fifth embodiment,a cross-sectional area of a mouth of the plunger cavity is substantiallysmaller than a cross-sectional area of the mold cavity.

Additional embodiments of the invention comprise any othernon-conflicting combination of features recited in the above-disclosedembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a conventional transfer molding apparatus.

FIG. 2A depicts part 200.

FIG. 2B depicts a composite molding apparatus for making part 200.

FIG. 2C depicts a first arrangement of fiber bundles, situated in theapparatus of FIG. 2B, for making part 200 of FIG. 2A.

FIG. 2D depicts a notional illustration of the distribution of fiberswithin part 200 based on the first arrangement of fiber bundles in FIG.2C.

FIG. 2E depicts a second arrangement of fiber bundles, situated in theapparatus of FIG. 2B, for making part 200 of FIG. 2A.

FIG. 2F depicts a notional illustration of the distribution of fiberswithin part 200 based on the second arrangement of fiber bundles in FIG.2E.

FIG. 2G depicts a third arrangement of fiber bundles, situated in theapparatus of FIG. 2B, for making part 200 of FIG. 2A.

FIG. 2H depicts a notional illustration of the distribution of fiberswithin part 200 based on the third arrangement of fiber bundles depictedin FIG. 2G.

FIG. 2I depicts the mold cavity of for making part 200 of FIG. 2A,showing vents at the terminus of the tines.

FIG. 2J depicts a timing diagram for actuating the vents and plungers ofthe mold cavity depicted in FIG. 2I.

FIG. 2K depicts the mold cavity of for making part 200 of FIG. 2A,showing vents at the terminus of the tines and along the side of thebody of the mold cavity.

FIG. 2L depicts a timing diagram for actuating the vents and plungers ofthe mold cavity depicted in FIG. 2K.

FIG. 3A depicts part 300.

FIG. 3B depicts a composite molding apparatus for making part 300.

FIG. 3C depicts a first arrangement of fiber bundles, situated in theapparatus of FIG. 3B, for making part 300 of FIG. 3A.

FIG. 3D depicts a notional illustration of the distribution of fiberswithin part 300 based on the first arrangement of fiber bundles depictedin FIG. 3C.

DETAILED DESCRIPTION

The following terms, and their inflected forms, are defined for use inthis disclosure and the appended claims as follows:

-   -   “Axial direction or Axially aligned” means, for example, in the        context of a plunger or plunger cavity, aligned with the stroke        direction of the plunger and, in the context of a mold cavity,        means aligned with the long(est) or major axis of the mold        cavity.    -   “Transverse or Transversely aligned” means, for example, in the        context of a plunger or plunger cavity, orthogonal to the stroke        direction of the plunger and, in the context of a mold cavity,        aligned with an axis that is rotated 90 degrees, in-plane, with        respect to the long(est)/major axis of the mold cavity.    -   “Out-of-plane” means, for example, in the context of a mold        cavity, aligned with an axis that is rotated out of the plane of        the major surface of the mold cavity. In embodiments of the        invention, the stroke axis of the plunger is out-of-plane with        respect to a major surface of the mold cavity.    -   “Fiber” means an individual strand of material. A fiber has a        length that is much greater than its diameter. For use herein,        fibers are classified as (i) continuous or (ii) short.        Continuous fibers have a length that is about equal to to the        length of a major feature of a mold in which they are placed.        And, similarly, continuous fibers have a length that is about        equal to that of the part in which they will reside. Short        fibers have a length that is shorter than the length of a major        feature of the mold in which they are placed, and typically        comparable to the length of minor features of the mold, plus        some additional length to enable “overlap” with other fibers,        such as continuous fibers. The term “short fiber,” as used        herein, is distinct from the “chopped fiber” or “cut fiber,” as        those terms are typically used in the art. In the context of the        present disclosure, short fiber is present in a preform and, as        such, will have a defined orientation in the preform, the mold,        and the final part. As used generally in the art, chopped or cut        fiber has a random orientation in a mold and the final part.        Additionally, as used herein, the length of “short fiber” will        be based on the length of the smaller features of a mold (they        will be comparable in length). In contrast, the length of        chopped or cut fiber typically bears no predefined relationship        to the length of any feature of a mold/part.    -   “Stiffness” means resistance to bending, as measured by Young's        modulus.    -   “Tensile strength” means the maximum stress that a material can        withstand while it is being stretched/pulled before “necking” or        otherwise failing (in the case of brittle materials).    -   “Continuous” fiber or fiber bundles means fibers/bundles having        a length that is about equal to the length of a major feature of        a mold in which the fiber/bundles are placed.    -   “Tow” means a bundle of fibers, and those terms are used        interchangeably herein unless otherwise specified. Tows are        typically available with fibers numbering in the thousands: a 1K        tow, 4K tow, 8K tow, etc.    -   “Prepreg” means fibers that are impregnated with resin.    -   “Towpreg” or “Prepreg Tow” means a fiber bundle (i.e., a tow)        that is impregnated with resin.    -   “Preform” means a sized, or sized and shaped portion of        tow/tow-preg, wherein the cross section of the fiber bundle has        an aspect ratio (width:thickness) of between about 0.25 to        about 6. The term preform explicitly excludes sized/shaped (i)        tape (which typically has an aspect ratio—cross section, as        above—of between about 10 to about 30), (ii) sheets of fiber,        and (iii) laminates.    -   “About” or “Substantially” means+/−20% with respect to a stated        figure or nominal value.

Other than in the examples, or where otherwise indicated, all numbersexpressing, for example, quantities of ingredients used in thespecification and in the claims are to be understood as being modifiedin all instances by the term “about.” Accordingly, unless indicated tothe contrary, the numerical parameters set forth in the followingspecification and attached claims are understood to be approximationsthat may vary depending upon the desired properties to be obtained inways that will be understood by those skilled in the art. Generally,this means a variation of at least +/−20%.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges encompassed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of about 1 and the recited maximumvalue of about 10, that is, having a minimum value equal to or greaterthan about 1 and a maximum value of equal to or less than about 10.

The fiber bundles that are sized or sized and shaped to form preformsfor use herein includes thousands of individual fibers, typically inmultiples of a thousand (e.g., 1 k, 10 k, 24 k, etc.). Such fiberbundles are typically called “tow.” In some embodiments, the fibers inthe tow are impregnated with a polymer resin; such material is referredto as “towpreg” or “prepreg tow.” Although all of the towpreg depictedin the Figures are cylindrical (i.e., have a circular cross section),they can have any suitable cross-sectional shape (e.g., oval, trilobal,polygonal, etc.).

The individual fibers can have any diameter, which is typically, but notnecessarily, in a range of 1 to 100 microns. Individual fibers caninclude an exterior coating such as, without limitation, sizing, tofacilitate processing, adhesion of binder, minimize self-adhesion offibers, or impart certain characteristics (e.g., electricalconductivity, etc.).

Each individual fiber can be formed of a single material or multiplematerials (such as from the materials listed below), or can itself be acomposite. For example, an individual fiber can comprise a core (of afirst material) that is coated with a second material, such as anelectrically conductive material, an electrically insulating material, athermally conductive material, or a thermally insulating material.

In terms of composition, each individual fiber can be, for example andwithout limitation, carbon, glass, natural fibers, aramid, boron, metal,ceramic, polymer filaments, and others. Non-limiting examples of metalfibers include steel, titanium, tungsten, aluminum, gold, silver, alloysof any of the foregoing, and shape-memory alloys. “Ceramic” refers toall inorganic and non-metallic materials. Non-limiting examples ofceramic fiber include glass (e.g., S-glass, E-glass, AR-glass, etc.),quartz, metal oxide (e.g., alumina), aluminasilicate, calcium silicate,rock wool, boron nitride, silicon carbide, and combinations of any ofthe foregoing. Furthermore, carbon nanotubes can be used.

Any thermoplastic can be used in conjunction with embodiments of theinvention. Exemplary thermoplastic resins useful in conjunction withembodiments of the invention include, without limitation, acrylonitrilebutadiene styrene (ABS), nylon, polyaryletherketones (PAEK),polybutylene terephthalate (PBT), polycarbonates (PC), andpolycarbonate-ABS (PC-ABS), polyetheretherketone (PEEK), polyetherimide(PEI), polyether sulfones (PES), polyethylene (PE), polyethyleneterephthalate (PET), polyphenylene sulfide (PPS), polyphenylsulfone(PPSU), polyphosphoric acid (PPA), polypropylene (PP), polysulfone(PSU), polyurethane (PU), polyvinyl chloride (PVC). An exemplarythermoset is epoxy.

The equipment used in conjunction with embodiments of the presentinvention have some similarities to a process known as “transfermolding.” FIG. 1 depicts conventional apparatus 100 for forming a partvia a transfer-molding process.

Apparatus 100 includes mold 102, mold cavity 104, transfer pot 106,sprue 108, plunger 110, heaters 112, and ejector pin 114, arranged asshown. A feed, which is usually a plastic/resin, is placed in transferpot 106. Plunger 110 is moved downwardly into transfer pot 106,compressing the plastic in the mold. Heaters 112 heat the mold to atemperature that is sufficient to melt the plastic. The liquid plasticthen flows through sprue 108 under pressure and into mold cavity 104.Sprue(s) 108 (there may be several) is typically a small cylindricalopening that leads from transfer pot 106 to mold cavity 104. After thepart is formed and the mold is opened, ejector pin 114 is used to pushthe part out of mold cavity 104. By virtue of the structural arrangementof the apparatus 100, such as the presence of the sprues, fiber,particularly continuous fiber, is typically not used in conjunction withthis transfer molding process. To the extent that the feed includes anyfiber, it is usually “chopped” fiber, so that it could fit through thesprue.

FIG. 2A depicts scoop 200. The scoop includes handle 202, body 204, andfingers or tines 206. Scoop 200 is very thin and has a relativelyelongated form. For a part having such a configuration, it is importantthat part stiffness and strength are oriented in the direction of thelong axis of the handle. This reduces any tendency for the part to snapunder flexion, such as could occur, for example, if tines 206 wereimmobilized in the ground and excessive upward or downward pressure isapplied at handle 202. It is also necessary that the tines are wellconnected to the handle via body 204 in strength and stiffness.

FIGS. 2B and 2C depict mold 210 for making scoop 200. The mold includesmold cavity 200′, including cavity portions 202′, 204′, and 206′ forforming respective portions of the scoop; that is, handle 202, body 204,and tines 206. Plunger 214 is received by plunger cavity 212 in mold210, and is arranged to move linearly therein. Note that stroke axis B-Bof plunger 214 is out-of-plane with respect to mold cavity 200′. Infact, stroke axis B-B is out-of-plane and orthogonal with respect tocavity portions 202′ and 206′.

In mold 210, as in many molds consistent with the present teachings:

-   -   the stroke axis of the plunger is out-of-plane with respect to a        major surface of the mold cavity by an amount within the range        of 45 to 90 degrees;    -   the cross-sectional area of the mouth of the plunger cavity is        substantially smaller than the cross-sectional area of the mold        cavity;    -   the length of the plunger cavity along the stroke axis is        substantially greater than a depth of the mold cavity.

The material that is used to form the part; that is, preforms 216′, arepositioned within plunger cavity 212 on a portion of mold cavity 200′;in this embodiment, on portion 202′. The embodiment shown in FIG. 2Cdepicts a first arrangement of preforms 216′, wherein the preforms areoriented horizontally, which is out-of-plane and, in fact, orthogonalwith respect to the plunger's stroke axis, B-B (i.e., the direction/axisalong which plunger 214 moves). Furthermore, preforms 216′ are axiallyaligned with mold cavity 200′; that is, they are aligned with axis A-A.

The number of preforms 216′ that are required for fabricating scoop 200(or any part) is determined by matching the mass of the preforms to themass of the fabricated scoop. In this embodiment, the length of preforms216′ matches the width of plunger cavity 212. The preforms could beshorter, but relatively longer fibers ultimately result in bettermaterial properties for the finished part.

FIG. 2D depicts a representation of the orientation of the fibers (frompreforms 216′) in the molded part; that is, scoop 200. Duringfabrication, fibers tend to flow along the direction of the long axis ofthe part, which is axis A-A in this embodiment. For this particularpart, the fibers follow the long axis of handle 202 before fanning outthrough body 204 of scoop 200, and ultimately flowing into tines 206.The fibers overlap, as illustrated, for example, at locations 218 and220, which provides considerable stiffness and strength to the scoop200. It will be appreciated that there are many more fibers, and manymore incidents of overlap thereof, in an actual part made in accordancewith the present teachings.

Furthermore, the degree of fiber overlap can be varied based on fiberlength and parameters that affect the final position of the fibers inthe mold cavity, such as vents. That is, sequencing the actuation ofvents 207 during the stroke of the plunger 214 can provide a stageddelivery of fibers. FIG. 2C depicts vent 207; one such vent isfluidically coupled to the terminus of each tine (only one is depictedin FIG. 2C) of the mold-cavity. Vents and their operation are discussedin greater detail in conjunction with FIGS. 2I through 2L, later in thisspecification.

FIG. 2E depicts, for the same mold 210, preforms 216″, which arearranged in a second arrangement that is different from the firstarrangement shown in FIG. 2C. In particular, preforms 216″ are orientedvertically, which is “axially aligned” with respect to the plunger'sstroke-axis B-B. Since, in mold 210, plunger cavity 212 is longer thanit is wide, preforms 216″ may be longer than preforms 216′ of FIG. 2C.As previously noted, longer fibers, such as are present in preforms 216″relative to preforms 216′, typically result in better materialproperties for the finished part.

Once again, vents (not depicted in FIG. 2E) are used to facilitate themovement of fibers to specific regions (e.g., the tines, etc.) andcontrol the extent of overlap with other fibers.

FIG. 2F depicts a representation of the orientation of the fibers (frompreforms 216″) in scoop 200. As in the embodiment depicted in FIG. 2D,the fibers tend to align with the long axis of the part, and overlap, asillustrated at location 222, for example.

FIG. 2G depicts, a third arrangement of preforms in mold 210, whereinrelatively shorter preforms 216′ are oriented horizontally and axiallyaligned with mold cavity 200′ (i.e., parallel to axis A-A), and preforms216″ are oriented vertically, axially aligned with the plunger cavity(i.e., parallel to axis B-B), and are positioned on top of preforms216′.

For very thin features, such as are present in scoop 200, it can bebeneficial to use such a combination of shorter fibers and longerfibers. The shorter fibers more reliably fill any thin/small/intricatefeatures. Meanwhile, the longer and shorter fibers intermingle andoverlap, thereby coupling the thin/intricate feature to the rest of thepart.

For example, in scoop 200, if mold filling is an issue, fibers fromshorter preforms 216′ at the bottom of the feed stack would flow firstinto cavity portion 206′ (the tines), and more easily fill this portionthan would longer fibers from preforms 216″. Although not depicted,vents, as previously discussed, are advantageously fluidically coupledto the terminus of each of the tines (i.e., mold-cavity portion 206′).Referring now to FIG. 2H, longer fibers 216 f″ from preforms 216″located higher in the feed stack would mix with shorter fibers 216 f′from preforms 216′, overlapping, such as at location 224, to connect thetips of tines 206 to the rest of scoop 200.

FIG. 2I depicts mold cavity 200′ without the surrounding mold 210. Vents207-1, 207-2, and 207-3 are individually fluidically coupled to theterminus of a respective tine. There are instances in which it will bedesirable to have fiber of a first characteristic fill some but not allof the tines of the mold cavity, whereas fiber having a secondcharacteristic fills the remaining tines.

For example, one or more of the tines may differ in length from theother tines, or one or more of the tines may experience greater stressesduring use than other of the tines. In such cases, the longer tines ortines experiencing greater stresses would benefit from relatively longerfibers, or fibers made from a relatively stronger material, or frommaterial having a relatively higher fiber-volume fraction.

To direct two (or more) groups of preforms having fibers that differ insome characteristic to different locations in a mold requires that thetwo (or more) groups of preforms be stacked in an appropriate order inthe plunger cavity. Thus, when the plunger is actuated (to force fiberand liquefied resin into the mold cavity), and an appropriate one ormore vents are actuated (to create a decrease in pressure at certaindiscrete regions of the mold cavity), fibers from the group of preformslowest in the plunger cavity enter the mold cavity (along with liquefiedresin) and flow to such discrete regions. After those discrete regionsfill, and with the plunger still moving downwardly, and one or moredifferent vents actuating, fiber from the next group of preforms in thestack (along with liquefied resin) enters the mold cavity and flow tofill other portions of the mold cavity that are at reduced pressure.

With continuing reference to FIG. 2I, and referring also to the timingdiagram of FIG. 2J, “Vent-1” corresponds to vent 207-1, “Vent-2”corresponds to vent 207-2, and “Vent-3” corresponds to vent 207-3.Vent-1 and Vent-3 control portions of the mold cavity that correspond to“the outer tines,” and Vent-2 controls the portion of the mold cavitythat corresponds to “the central tine.” The central tine is to be filledfirst, followed by the outer tines, then the rest of the mold cavity. Anappropriate amount of a first type of preforms for filling the centraltine is placed at the bottom of the plunger cavity. An appropriateamount of a second type of preforms for filling the outer tines isplaced on top of the first type of preforms. Additional preforms wouldbe placed on top of the second type of preforms for filling the balanceof the body (204′) and handle (202′) portions of the mold cavity.

At time T₁, the plunger (e.g., plunger 214, FIG. 2G) is actuated, movingdownwardly to force fibers and now-liquefied resin into mold cavity200′. Also at time T₁, Vent-2 is actuated (i.e., opened). Actuation ofthis vent creates relatively lower pressure in the central tine ascompared to the outer tines. Consequently, fibers and resin flow to fillthe central tine. By time T₂, the central tine has filled with resin andthe appropriate type of fiber, and Vent-1 and Vent-3 are actuated tocreate relatively lower pressure in the outer tines versus the centraltine and other regions of the mold cavity. Note that the plunger isstill moving downwardly, forcing fiber and liquefied resin into the moldcavity. Although FIG. 2J depicts Vent-2 being closed at time T₂, that isnot necessary, since as a region fills with material, the pressure itwould take to force further fiber into the region increasessignificantly. The fiber and resin will thus preferentially flowelsewhere; in this case, to the outer tines.

Actuation of later-opened vents (such as Vent-1 and Vent-3) can becontrolled passively, using relief valves on the vents, for example. Insuch an embodiment, when the pressure in the mold cavity exceeds somevalue (as discrete regions fill while fiber and resin continue to beforced into the mold cavity), the relief valve actuates, thereby openingthe initially closed vent. Alternatively, the vents can be activelycontrolled, such as by using position control on the plunger andcontrolling for volume. That is, knowing how much material is forcedinto the mold cavity per unit movement of the plunger, and how muchmaterial must be delivered to fill portions of the mold cavity that areto be filled first, one can determine the requisite change in positionof the plunger to deliver that amount of material. Thus, once theplunger moves the determined amount, a second set of vents are actuated.

FIG. 2K depicts mold cavity 200″, which is another embodiment of a moldfor making scoop 200 of FIG. 2A. In addition to having a vent at theterminus of each tine, mold cavity 200″ includes four vents 207-4,207-5, 207-6, and 207-7, two of which are fluidically coupled to eachside of body portion 204′ of the mold cavity. These vents can be used tocreate a crossing overlap between fibers in the tines and fibers inother portions of the scoop.

FIG. 2L depicts a timing diagram that illustrates a mold-fillingprocess. For this example, it is assumed that the tines receive one typeof fiber, and the rest of the mold receives a second type of fiber. Thefibers that are primarily intended for the tines are about 1.5 timeslonger than the tines. The fibers that are primarily intended for thebalance of the mold cavity are about 2.5 times the length of the tines.A first group of preforms having fibers intended for the tines areplaced into the plunger cavity, followed by a second group of preformshaving fibers intended for the rest of the mold cavity. Relativelyshorter preforms 216′ and relatively longer preforms 216″ shown stackedin the plunger cavity in FIG. 2G is illustrative.

The amount of fiber and resin in the first group of preforms issufficient to fill the tines. The second group of preforms includes thefiber and resin required to fill the rest of the mold cavity.

By time T₁, the resin in at least the first (lower) group of preforms isliquefied. At time T₁, the plunger as well as Vent-1, Vent-2, and Vent-3are actuated. The relatively lower pressure in the tines draws therelatively shorter fibers from the first group of preforms into thetines.

At time T₂, Vent-4, Vent-5, Vent-6, and Vent-7 are actuated, created lowpressure regions to the sides of mold body portion 204′. The plungercontinues its downward movement, forcing fiber from the second group ofpreforms as well as liquefied resin into the mold cavity. The portion ofthese longer fibers that reside in body portion 204′ tend to curvetoward either of the sides thereof, crossing the portion of fibersextending from the tines. As previously discussed, the vents need not beclosed when the cavity portions they control are filled since it wouldtake a substantially increased pressure to force additional materialinto those regions.

FIG. 3A depicts bracket 300. The bracket includes body 302, fourhorizontal tabs 304, fastener holes 306, two vertical tabs 308, androd-receiving holes 309. Bracket 300 can be used, for example, toconnect a rod end to a control surface. The rod is received byrod-receiving holes 309. Fastener holes 306 mount bracket 300 to asurface with screws, bolts, pins, etc. Vertical tabs 308 and horizontaltabs 304 are orthogonal to one another. It is desirable to have goodbending stiffness in each of tabs 304 and 308 and for all of such tabsto be well connected to one another in strength and stiffness.

FIGS. 3B and 3C depict mold 310 for making bracket 300. The moldincludes mold cavity 300′. Plunger 314 moves linearly along stroke axisB-B (FIG. 3C) in the plunger cavity in mold 310. Otherwise hidden linesof mold 300′ are depicted to show how the part is situated in the mold.Parting lines on the mold have been omitted. Once again, stroke axis B-Bof plunger 314 is out-of-plane with respect to mold cavity 300′ and, inparticular, to body portion 302′ and horizontal tab portions 304′thereof. Mold 310 also includes sliding pins (not depicted for the sakeof clarity) to create holes 306 and 309.

As depicted in FIG. 3C, the preforms that will form the part areorganized to have two different orientations in the plunger cavity.Preforms 316′ at the bottom of the stack of bundles are aligned withaxis A-A, which is the long axis of mold cavity 300′. In other words,fiber bundles 316′ are axially aligned with respect to mold cavity 300′.Preforms 316″ at the top of stack are aligned with axis C-C, which istransverse to the long axis of mold cavity 300′.

FIG. 3D depicts a representation of the orientation of the fibers (frompreforms 316′ and 316″) in bracket 300. As implied above, the fibersfrom the preforms flow into mold cavity 300′ in the order in which theyare positioned in the plunger cavity, those on the bottom (i.e., on thesurface of mold cavity 300′) flowing first.

Thus, fibers 316 f′ from lower, axially-aligned preforms 316′ willpreferentially fill horizontal tab portions 304′ (FIG. 3B) of the moldcavity first, which are generally aligned with axis A-A. Fibers 316 f″from transversely oriented preforms 316″ begin filling mold cavity 300′after all fibers 316 f′ from preforms 316′ have flowed into the moldcavity. The intent is to have fibers 316 f″ filling vertical tabs 308.The transverse orientation of fibers 316 f″ is not to promote flowtoward vertical tabs 308; rather, it is to facilitate an overlap withaxially running fibers 316 f′.

Preforms follow the path of least resistance, which typically meansflowing along the long axis of the mold cavity and towards regions oflowest pressure. The latter parameter—pressure—can be altered throughthe use of strategically located vents, as previously disclosed. Thistechnique can be used to selectively direct the flow of resin and fibersto a particular location.

Thus, in the present embodiment, vents (not depicted) are situated tovent pressure at the terminus of horizontal tab portions 304′ and at thetop of vertical tab portions 308′ of the mold cavity (FIG. 3C). In someembodiments of the invention, after fibers 316 f′ from preforms 316′flow to horizontal tabs portions 304′, the vents controlling thepressure at those locations are closed and the vents controlling thepressure at the tip of vertical tab portions 308′ are opened. Thiscreates a region of relatively lower pressure at the tips of thevertical tab portions of the mold cavity, and resin/fiberspreferentially flow toward those locations.

As a consequence of vertical tabs 308, it is likely that gravity willresult in resin/fiber flowing preferentially to horizontal tab portions304′ and then, as the level of resin rises, fibers/resin will eventuallyflow to vertical tab portions 308′. Although some mixing will occur,fibers 316 f″ from bundles 316″ will primarily end up in vertical tabs308, aligned with the axis C-C (see FIG. 3D).

Mixing between fiber orientations occurs near the middle of bracket 300,such as at location 320. This facilitates strong connections between allfeatures of bracket 300. And overlap between fibers flowing around holes306 in different directions, such as at location 322, results in goodhoop strength for those features.

Fiber bundles at other angles (i.e., not aligned with axes A-A or C-C)could also be included. In some embodiments, axially aligned preforms316′ are made from carbon fiber towpreg and transversely alignedpreforms 316″ are made from glass fiber towpreg, both incorporating thesame resin. This results in vertical tabs 308 being more compliant thanhorizontal tabs 304. Moreover, fiber volume fraction could be variedacross the stack to engineer different material properties for differentportions of bracket 300.

In a further embodiment, part strength is increased in select areasusing a preform that is placed in mold cavity 300′ prior to flowing thepreforms into the mold cavity. For example, if an amount of hoopstrength is required that is greater than what is nominally expectedfrom the methods disclosed herein (i.e., that which results from theoverlap of flowing fibers coming from both sides of fastener holes 306),a helical, spiral, or circular fiber-bundle preform, such as preform318, is placed around one or more of holes 306. The flowing fibers fromthe method described herein overlap and couple to preform 318 andconnect it to the rest of the part during the molding process.

In accordance with the present method, to fabricate scoop 200 (FIGS.2A-2L) or bracket 300 (FIGS. 3A-3D), the mold parts are combined(closed), except for the plunger, leaving the plunger cavity open. Thefinal weight of the part is estimated from part volume and the densityof the composite material. Maximum length(s) for the fibers aredetermined as a function of its intended location and orientation in themold cavity. The maximum length for preforms is determined as a functionof its orientation in the plunger cavity. Preforms are created bycutting towpreg in appropriate lengths, recognizing that the allowablelength of a fiber, as calculated based on its orientation in the mold,might be longer than its actual length, as determined and permittedbased on the size of the plunger cavity.

All fibers are weighed to check that the weight of the fiber/resinmatches the expected final part weight. The total weight of the preformscan slightly exceed the expected part weight since some of the resin,and even fiber, will flow into the vents of the mold.

Preforms are then stacked in the plunger cavity in the requisite orderand orientation. The plunger is then placed in the plunger cavity. Theentire mold, including the plunger cavity, plunger, and mold cavity areheated. In some embodiments, cartridge heaters or the like, which areinserted through holes into the mold, are used to heat the plunger, theplunger cavity, and the mold cavity. In some other embodiments, the moldis situated on a heated platen, which is used to heat the mold. Forlarge molds, an insulating blanket can be placed around the mold toreduce radiative and convective heat losses. In most embodiments inwhich plural groups (different types) of preforms are used, there is noneed to differentially heat the different groups of preforms. Dependingon the manner in which the preforms are stacked, after mixing in theplunger cavity of different fibers from different preforms is minimal.To the extent it may, in certain applications, be desirable to melt onetype of preform before another type, this can be accomplished byoperating the mold cavity at a higher temperature than theplunger/plunger cavity.

After heating, the plunger is pressed against the preforms, therebycompressing the fibers and resin and forcing them into the mold cavity.After an appropriate amount of time under heat and pressure inaccordance with compression molding protocols, heating ceases. In someembodiments, the mold is actively cooled, such by passing air, water,steam, or oil through cooling channels. After cooling, the mold isdisassembled, as necessary, to remove the composite part formed by thisprocess.

It is to be understood that the disclosure describes a few embodimentsand that many variations of the invention can easily be devised by thoseskilled in the art after reading this disclosure and that the scope ofthe present invention is to be determined by the following claims.

What is claimed:
 1. A method for compression molding utilizing a plungercavity that is fluidically coupled to a mold cavity, and a plungerreceived by the plunger cavity, the method comprising: advancing theplunger in the plunger cavity to force fibers and resin into the moldcavity; and actuating, in sequence, a first vent that is fluidicallycoupled to a first region of a mold cavity, and a second vent that isfluidically coupled to a second region of the mold cavity, wherein thesequenced actuation of the first and second vents causes, in sequence, afirst group of the fibers to preferentially flow to the first region ofthe mold cavity, and a second group of the fibers to preferentially flowto the second region of the mold cavity.
 2. The method of claim 1wherein fibers and resin forced into the mold cavity are sourced from afirst group of preforms and a second group of preforms that are placedin the plunger cavity, and wherein the method comprises ordering thefirst group of preforms and the second group of preforms in a stackwithin the plunger cavity.
 3. The method of claim 2 wherein orderingcomprises positioning the first group of preforms in the plunger cavityso that the first group of fibers, which are sourced from the firstgroup of preforms are forced into the mold cavity before the secondgroup of fibers, which are sourced from the second group of preforms. 4.The method of claim 2 wherein the method comprises: placing the firstgroup of preforms in a first orientation in the plunger cavity; andplacing the second group of preforms in a second orientation in theplunger cavity, wherein the first orientation is different than thesecond orientation.
 5. The method of claim 1 wherein the first group ofpreforms and the second group of preforms differ from one another as toat least one characteristic.
 6. The method of claim 5 wherein the atleast one characteristic is selected from the group consisting of (i) alength of fibers, respectively, in the first and second groups ofpreforms, (ii), a composition of the fibers, respectively, in the firstand second groups of preforms, and (iii), a fiber volume fraction,respectively, in the first and second groups of preforms.
 7. The methodof claim 2 comprising coordinating the ordering of preforms in theplunger cavity with the sequencing of vent actuation so that the firstgroup of fibers, which are sourced from the first group of preforms,enter the mold cavity before the second group of fibers, which aresourced from the second group of preforms, thereby ensuring that uponactuation of the first vent, the first group of fibers flow to the firstregion of the mold cavity.
 8. A method for compression molding utilizinga plunger cavity that is fluidically coupled to a mold cavity, and aplunger received by the plunger cavity, the method comprising: stackinga first group of preforms and a second group of preforms in the plungercavity in a first order, each preform in the first group and the secondgroup comprising resin-coated fibers, and wherein the first group ofpreforms and the second group of preforms differ from one another as toat least one characteristic; advancing the plunger in the plunger cavityto force fibers and resin from the first group of preforms and thesecond group of preforms into the mold cavity in accordance with thefirst order; and actuating, in sequence, a first vent that isfluidically coupled to a first region of a mold cavity, and a secondvent that is fluidically coupled to a second region of the mold cavity,wherein the sequence of vent actuation is coordinated with the orderedmovement of the fibers and resin into mold cavity so that fibers fromthe first group of preforms flow to the first region and fibers from thesecond group of preforms flow to the second region.